It
has the two pieces type bayonet.So it will need a special Leitax bayonet.

Remove the three bayonet screws .

And you can lift the bayonet now.

To remove the 1st. black ring, this spring must go.The needle with hook is very useful here.

Be careful, we don't want the spring to jump.

Now we can lift the 1st. ring, pay attention to the position of the lever, as we are going to put it again later..

And now the 2nd. ring, we are not going to use this one later.

This button must go too, as it cannot fit it place with the Leitax bayonet.

Now we are going to put the 1st. ring only. Check if it is ok rotating it, with the aperture ring at 16, the iris must open and close.

This is the special Leitax bayonet for OM lenses with two piece bayonet.

This
special bayonet will press the 1st. ring , first screw it lightly so
you can still move the ring, rotate it until the iris is closed.If you continue screwing the bayonet, it will keep the 1st ring to this correct position.Now the aperture ring will make the iris open and close.Enjoy!

As you can see, we have to cover the hole where that button was.

In case that screwing firmly the
bayonet, the ring doesn't stay firm in place, you can bend it slightly,
just a little bit, so little that you wont notice the bending visually.

Now put it again and it will stay firm in place, and the iris will open and close when you rotate the aperture ring.